Scale deposition, inhibitors

Uses Scale/deposit inhibitor and dispersant for use in phosphate and zinc-based... 

Scale Inhibitors. When scaling conditions exist, scale inhibitors can be used to control the scaling tendencies, and keep metal surfaces free of scale deposits. Scale inhibitors are chemicals that interrupt and deform the normal crystalline growth pattern of carbonate scales. The three most commonly used classes of scale-inhibiting chemicals used in drilling fluid are [191,197] ... 

Scale formation Controlled scale deposition by the Langelier approach or by the proper use of polyphosphates or silicates is a useful method of corrosion control, but uncontrolled scale deposition is a disadvantage as it will screen the metal surfaces from contact with the inhibitor, lead to loss of inhibitor by its incorporation into the scale and also reduce heat transfer in cooling systems. Apart from scale formation arising from constituents naturally present in waters, scaling can also occur by reaction of inhibitors with these constituents. Notable examples are the deposition of excess amounts of phosphates and silicates by reaction with calcium ions. The problem can be largely overcome by suitable pH control and also by the additional use of scale-controlling chemicals. 

Kinetic inhibitors for hydrate formation may also be effective in preventing scale deposition [1627]. This may be understood in terms of stereospecific and nonspecific mechanisms of scale inhibition. 

Acids, when used as scale inhibitors, are extremely corrosive. Their effectiveness has been laboratory tested. Parameters include acid type, metallurgy, temperature, inhibitor type and concentration, duration of acid-metal contact, and the effect of other chemical additives [279]. Lead and zinc sulphide scale deposits can be removed by an acid treatment [922]. 

Optimum savings in cooling water consumption and inhibitor usage (and hence savings in cost) can be effected by running the COC of any cooling system as close to the theoretical maximum as possible. However, the risks of scale deposition and other problems can increase dramatically. Therefore, plans for raising the COC should only consider the practical maximum COC, which is a lower level. 

Amersperse. [Drew Ind. Div.] Evapora-tor/vacuum pan scale and deposit inhibitor. 

Scaleclean F. [Stewart H ] Scale and deposit inhibitor for potable water systems. 

Belclene . [Ciba-Geigy] Algicides for water treatment scale and deposit inhibitor. 

Obviously when we deliberately add sulfuric acid to cooling water, we reduce alkalinity and also depress pH. This increases corrosivity of the circulating water, which is saturated with dissolved oxygen, contacts many dissimilar metals, and is elevated in temperature. In the process of acidification to prevent scale deposition so heat transfer equipment will function efficiently, we knowingly build in added corrosion factors and increase corrosion control difficulty. Now we need to find corrosion inhibitor combinations which will be practical for use in industrial systems can be tolerated from the viewpoints of toxicity and pollution controls and will effectively protect these multimetal circuits during their normal service life of 20 to 30 years. 

Uses Corrosion/scale inhibitor used in various aq. systems (boiler feed water, recirculated cooling water) over wide temp, range dispersant for dyes, pigments, latex paints food pkg. adhesives, paper/paperboard Features Inhibits scale deposits on equip, surfs., promotes efficient heat transfer, decreases equip, damage Reguiatory FDA 21CFR 175.105,176.180 Properties Pale yel. clear liq. m.w. 15,000 dens. 9.2 Ib/gal vise. 19-182 cps f.p. 28 F pH 9.5-10.5 (10% aq.) surf. tens. 64 dynes/cm (0.1%) 24-26% total solids... 

Uses Scale inhibitor for cooling water systems, boilers, and in oil fields to control calcium, barium, magnesium, strontium, and iron scale deposits... 

Sodium polyphosphate is often used in a concentration of about lO-lOOppm, sometimes with added zinc salts to improve inhibition. The pH value is adjusted to 5-6 in order to minimize pitting and tubercle formation, as well as scale deposition. Polyphosphates decompose slowly into orthophosphates, which, in the presence of calcium or magnesium ions, precipitate insoluble calcium or magnesium orthophosphate, causing scale formation on the warmer parts of the system. Unlike chromates, they favor algae growth, which necessitates the addition of algaecides to the water. Corrosion inhibition with polyphosphates is less effective than that by chromates, but polyphosphates in low concentration are not toxic, and the required optimum amount of inhibitor is less than that for chromates. 

Scale inhibitor Ethylene glycol Prevents scale deposits in pipes Automotive antifreeze, household cleansers, deicing agent... 

Figure 13. Relationship between scale deposit and concentiation of additives added (supersaturation ratio 3.05, flow rate 2 ml per second, temp. 20 C. coupon stainless steel, length 3 cm, diameter 1.3 cm. inhibitor a. EDTP, b. NTMP, c. NDPA. run time 4 hours)...

In 1928, the use of acidizing rose again, albeit briefly. The Gypsy Oil Company, a subsidiary of Gulf Oil Company, used HCl to remove calcareous scale deposited, in the pipe and on equipment, in Oklahoma wells. Treatment recommendations for these wells were provided by Dr. Blain Westcott of the Mellon Institute at the request of Gypsy Oil. Interestingly, his recommendations included the use of Rodine No. 2, an acid corrosion inhibitor used in acid pickling in steel mills. 

Uses Corrosion, scale fonnation inhibitor used in oil well operations Features Synergistic ability to disperse, degrade and prevent paraffin deposition ... 

Chem. Descrip. Blend of polymeric dispersants, a defoamer, and antisealants Uses Scale inhibitor and antifoam for aqueous systems very effective in steam boilers where suspended solids must be dispersed and antifoam is needed to control priming or foaming problems it will inhibit scale forniation at low dosages at high dosages, old scale deposits can be removed while unit remains in operation... 

Chem. Descrip. Syn. and org. polymers and zinc corrosion inhibitors Uses Cooling water treatment, corrosion/scale inhibitor, dispersant for cooling towers cleans existing scale deposits and prevents further scaling Features Rec. for cooling towers utilizing makeup water that is < 10 grains/gal (170 ppm) total alkalinity... 

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